1. Field of the Invention
The present invention relates to a capacitive touch panel and a display device using the capacitive touch panel. Specifically, the present invention relates to a capacitive touch panel having low coupling capacitance and a display device using the capacitive touch panel.
2. Description of the Prior Art
Display panels and flat screen display device using the display panels are gradually becoming the mainstream in the field of display devices. For instance, flat television for home use, liquid crystal display of the personal computer or of the laptop computer, display screen of mobile phone and digital camera are products incorporating the display panel as one essential component. As the product design is gradually becoming user-oriented, the usability for the user and the touch input function of the display panel become an emphasis in the development of display device industry.
As FIG. 1a shows, a conventional liquid crystal display (LCD) panel with touch-input function includes a display panel 10 and a touch panel 30. The touch panel 30 is disposed on the display surface 11 of the display panel 10. In other words, the images are displayed outwards through the touch panel 30. Currently the majority of touch panel 30 include resistive and capacitive touch panels.
As for the resistive touch panel 30, the operation principle includes using the voltage drop within the resistive touch panel 30 to locate the coordinates of the contact point. The touch panel 30 is composed of an upper layer and a lower layer. The touch panel 30 applies a voltage across the two layers. When the user physically points at the touch panel 30, a conducting loop is created at the contact point. The voltage drop within the conducting loop is used by the system to determine the location of the contact point. However this type of touch panel 30 cannot process multi-input simultaneously and also cannot process fingerprint recognition. Furthermore, a minimum applied pressure is required to create a conducting loop at the contact point, and thus the resistive touch panel 30 is subject to a minimum applied pressure.
The operation principle of capacitive touch panel 30 is different from that of resistive touch panel 30. As for the conventional capacitive touch panel shown in FIG. 1b, X direction electrodes 31 and Y direction electrodes 31 are disposed at an upper and a lower layer respectively. When the user physically contacts the touch panel 30 with fingers or other conductive objects, a difference in capacitance is created at the touch panel 30. The system will be able to determine the contact point based on the difference in capacitance. As FIG. 1b shows, the conventional capacitive touch panel 30 uses quadrilateral electrodes 31. The lateral sides of electrodes 31 on the same or on different electrode layers have longer effective corresponding length between electrodes 31. The distance between electrodes 31 is not changed and this creates a larger effective overlapping area for creating capacitance between electrodes 31. As the lateral capacitance between electrodes increases, the system's overall coupling capacitance also increases which in turn increases the overall loading of the system.